The present invention relates to air pilot cartridge valves, and more particularly relates to an air pilot cartridge valve that can be disassembled and repaired, and also that resists leakage during high back pressure and additionally that is configured to actuate against high back pressure.
Air pilot operated cartridge valves have been used for many years, and are commercially available, such as through Doering Company. The known Doering air pilot operated cartridge valve includes an actuator (also called an “operator” herein) incorporating a single acting return air cylinder and a cartridge valve section with single-stem poppet. The cartridge valve section is designed to fit a standard hydraulic valve 8-2 size cavity. The cartridge valve section's body includes a hex to receive a wrench to facilitate installation. Rotating the hex on the valve section threads the valve into the cavity. The air pilot operator is free to not rotate with the hex.
The above known air pilot operated cartridge valve has at least three major faults. Its single air piston must be large enough to provide the area for the force necessary to move the poppet off the seat. However, this is especially a problem when the poppet return spring has to have enough force to keep the poppet on the seat when high pressure is on the output port 2 instead of input port 1, or when pressure on output port 2 is higher than pressure on input port 1. Also, the poppet seal and air pilot operator in the known air pilot cartridge valve are so difficult to replace that the valve is considered to be a “throw away”. Even the manufacturing company will not repair these valves. Still further, construction design and assembly methods are press fits, such they do not allow space for a replaceable poppet seal.
More specifically, a large 1⅞″ diameter air pilot operator is necessary when the valve must stop high back pressure flow from a (normally output) port 2 to a (normally input) port 1. However, larger diameter air pilot sections limit installation options, since such valves are often used in very tight locations on a control manifold.
Also, air pilot operated cartridge valves are often used as hydraulic valves or valves for high viscosity fluids. For example, I have used them in automatic apparatus lubricating grease systems. In fact, many of my dispensing systems are being used for materials that have an apparent viscosity similar to grease, but that are not lubricating grease. Some of these materials such as anti-seize compounds contain abrasives that can damage dynamic resilient seals. When used to dispense anti-seize compounds, the poppet seal in the known valve can wear out in less than 250,000 cycles (which is costly and a problem since it is not replaceable).